Top 11 compounds in US drinking water

A comprehensive survey of the drinking water for more than 28 million Americans has detected the widespread but low-level presence of pharmaceuticals and hormonally active chemicals.

Little was known about people's exposure to such compounds from drinking water, so Shane Snyder and colleagues at the Southern Nevada Water Authority in Las Vegas screened tap water from 19 US water utilities for 51 different compounds. The surveys were carried out between 2006 and 2007.

The 11 most frequently detected compounds - all found at extremely low concentrations - were:

Atenolol, a beta-blocker used to treat cardiovascular disease

Atrazine, an organic herbicide banned in the European Union, but still used in the US, which has been implicated in the decline of fish stocks and in changes in animal behaviour

Carbamazepine, a mood-stabilising drug used to treat bipolar disorder, amongst other things

Estrone, an oestrogen hormone secreted by the ovaries and blamed for causing gender-bending changes in fish

Gemfibrozil, an anti-cholesterol drug

Meprobamate, a tranquiliser widely used in psychiatric treatment

Naproxen, a painkiller and anti-inflammatory linked to increases in asthma incidence

Phenytoin, an anticonvulsant that has been used to treat epilepsy

Sulfamethoxazole, an antibiotic used against the Streptococcus bacteria, which is responsible for tonsillitis and other diseases